Method of separating tin compounds from solutions



J an. 7, 1930. H. M. SCHLEICHER 1,742,284

METHOD OF sEARATINq' TI-N COMPOUNDS FROM sommo'ns Filed Nov. 6, 1925 2 Shgets-Sheet 1 -50LUT/0H OF I I .7 7 50L 7/0 j 2 H l I I SODIUM ARSENAIE l A ARSEN/(I 7 l2/ EXCEss REAGENT CHALK+ TIN Pm; SPQNT PRECIPITATE .SOLUT/Q 0 SOLUTION .SDPIUM A RSENATE INVENTOR 7 714. Sa a- 4 Za'ATTORNEYS Jan. 7, 1930. H. M. SCHLEICHER METHOD OF SEPARATING TIN C CSMPOUNDS FROM SOLUTIONS 2 Shets-Sheet. 2

Filed Nov. 1925 f INVENTOR 7/. S ZMQQ I ATTORNEYS Patented Jan. 7, 1930 UNITED STATES? PATENT OFFICE HENRY M. SCHLEICI-IER, or Mo TEREY, MEXICQ, AssIeNon r0 AMEnIoAN Nm'rAL ooMPANY, rn, on NEW YORK, N. Y., A oonronA'rIoN on NEW YORK METHOD or sErARATING TI ooMPoUNns FROM soLU'rroNs -A pp1ication filed fiovember'fi, 1925. Serial No. 67,224. l I

This." invention relates to conducting.

chemical reactions and particularly to the separation of tin compounds from solutions.

In carrying out such reactions it is desirable frequently to precipitate thejconstitucuts of solutions selectively and this involves;-

sometimes the careful proportioning of the added reagent to prevent either the preci 1 tation of a second constituent or the inc 11. sion of an excessof the reagent in the precipa itate. In certain cases, forexam'ple, the-ad. dition of the minimum amountof the re agent to precipitate one GOIlStltllBDtWlllxaCA.

tually cause precipitation of a of another constituent; It may possible to avoid this result by using an excess of the reagent with the result, however, that "the I recipitate will include some of this excess.

either alternative is desirable.

It is the object of the present invention to provide a method of carrying out reactions of the character described in the separation of tin compounds from solutions whereby the desired precipitate can be obtained in substantial purity free from contaminating constituents'of the solution treated and ofthe reagent.

. Further objects and advantages'of the in vention-will be apparent as it is better understood by reference to the following specification and accompanying drawing," in

which.

ing out the process;

7 one type of agitating tank adapted, to be other type of agitating tank; and

section through an Fig. Gis 'a vertical section structure illustrated in Fig. 5.

It is desirable in-certain operations to precipitate tin from solutions containing sodium through the stannate and sodium arsenate. The tin can i be precipitated by the addition of chalk (calc'ium carbonate) which may be added in the ]proportion I bewithdrawn from the process. r

Fig. 1 is a diagrammaticillu'stration of an apparatusadapted to-- be used in carry- Fig. 2- is a longitudinal section through solid state or in suspension to the solution; Unfortunately if only so much chalk is'added as is capable of precipitating all of the tin a certain amount of arsenic Willalso be precip'itated and will contaminate the tin. It is desirable to avoid the presence of arsenic; ,This

cess ofchaIk, but the precipitate will include steps, the first involving the addition of onl about one-half'of the total amount of chal required to precipitate the tin. The precipitate obtained by this part of the operation is free from arsenic .because' under the conditions'of concentration of the tin and chalk the 'arsenic'is prevented from separating from can be accomplished by the use of alarge exthe solution. The precipitate containing. only the tinxis separated from the solution which amount jofchalk which would have been re- 'Y is then treated in the second step with the full quired to precipitate all of the tin originally I in the solution." Inother words, the excessof chalk is about equal to the amount actually required to separate the tin remaining in the solution. This excess ofchalk prevents the precipitation of arsenic and the precipitate obtained contains all of the tin present in the solution mingled with the excess reagent.

The solutionwhich is now free-from tin It will be -seen that the precipitate obtained the tin in agsolution having the concentration of the solution originally treated. Consein the second stage contains about-half the total amount of chalk required to precipitate quently this mixture of chalk and tin can be. I

used asth'e-rea'gent in precipitating tin from a new batch ofithe solution and the precipitated 'tiirwill join that which has already separated'wi'ththechalk leaving a solution containing" approximately half of the tin with the arsenic. This solution is-then treated withanexcess of chalk as before to again obtain a mixture containing the tin with the reagent, thus completing the second cycle of operation. This cycle can be carried on indefinitely by introducing the fresh solution and the reagent at the properpoints and will re.

sult a solution free from tih and cbntaining all of .the arsenic andafprecipitate containing all ofthe tin and free from arsenic.

The proportions of the reagent to be added in the"-twbsteps ofnthe process are preferably, asji'ndioa'ted, but variation from these proportions 'is pernii'ssihlelf Thus, if less than half oflthe' reagent is added in the first step more than half will be added "in-the secnd step and likewise the addition of'more than half of the reagent in the first step will require a corresponding reduction in the amount added inthe second step. It is necessary only to so proportion the amountof reagent added'in thefirst step that the nude sirable constituents of the solution are not precipitated therebyv In carrying. out the invention an apparatus such as that indicated'in Fig.1 is employed preferably, It comprisesa plurality of boxes of suitable construction to hold the solutions, the boxes being separate except for in.-

lets and outlets permitting theflow of the solutions therethrough. If the reaction requires the application of heat the solutions may be heated bcforeth-ey are introduced and the boxes may be suitably insulated. Other wise it may be necessary to mount the boxes in asuitable furnace to permit the application ofheat thereto or heating coils supplied by steam d'f' other heating medium ay be utilized therein. As indicated, the boxes are i arranged in two series of three each so that one solution. flows in' one direction whi-leithe other flows in; the opposite direction "throu gh fthe separateseries. At the opposite ends of the apparatus suitable separators are provided, to permit the withdrawal of the liquid from the precipitate.- The well known Dorr thickener indicated at '6 is adapted for such .9usebutother separating devices may be em.-

ployed: The boxes 5 are provided With suitable stirring devices 7 to maintain an active agitation of the contents. The freshsolution 1 stitutedthe precipitate would remain in the is introduced at 8-:and }flows-Isuccessively through the boxes on one sideoi' the apparatus, being discharged at an overflow 9, at

the opposite end of that series.., Th s con-' veyed to the thickener 6 which is of the usual construction and .is'therepeimitted to settle,

the finished precipitate being-withdrawn from the bottom of the apparatus as isu'siial' in. thickening--operations: If a filter is .sub

filter after the solution had heenreinoved.

The solutionfrom which approximately half either as asolid or in suspension in a suitable liquid isintrodu'ced and mingled with the solution from the thickener. T hemix- .ture continues through' the series of boxes separated escapes and escapes through'an overflow 11 through the secondthickener 6 or the equivalent filter. I

Inthe thickener the precipitate which in solution together with the excess of reagent is withdrawn through the bottom and is de-' livered atthe inlet 8 with the fresh'solution' Jcl'udesall of'the desired constituent of the to the other series of .boxes. The solution from whichthe' desired constituent has been through an overflow 12 from the thickener. Thus it will be seen that one of the thickeners discharges the finished precipitate which may be treated thereafter in any desired manner for the further purification or recoveryof the desired constituent while the other thickener discharges the solu- 1 tion freed from the desired constituent. This solution can be treated thereafter for the recovery of any constituents remaining therein. I In case tin is separated from asolution containing sodium stannate and sodium arsenate, in the first'series of boxes approximately-onehalfof the tin content of the solution will separate and the precipitate containing only the tin will be withdrawn from the thickener, leaving the solution containing the remainder of the tin and the arsenic to be treated with the excess of fresh reagent, i. e.,

chalk, in the second series of boxes. The

.precipitate obtained therein will include the remainder of the tin free from arsenic and the excess of chalk, and this is separated in (the second thickener and added at the inlet 8 to the apparatus where it is mingled with the fresh solution. I

It is essential thatv the solution be thoroughly agitated during the precipitation and also that all of the solution remain in the individual boxes fora sufiicient time to ensure a thorough reaction. A preferred form of the boxesis. illustrated in Figs. 2 to 4 of thedrawing, in which a shell 13 is provided with. a cover l t and is separated by partitions-15 into a plurality of compartments constituting, the separate boxes. A shaft 16 extends through the" compartments and is adapted to be driven through apulley 17,

for example, from a suitablesource of power. Paddles 18 are mounted at intervals on the shaftto operate-in eachof the compartments, the paddles being. provided with. discs 19 at their opposite sides to ensure the passage of the liquid; through the compartments in succession. as indicated by the arrows therein;

- The discs prevent the solution from passing directly through the several compartments Which are connected by openings 20 and thus ensure proper conduct of the reaction. An overfiow21'permits the escape of the solution after'pa-ssing through the several compartments; lit-will be understood that there are two sets of compartments as hereinbefore indicated, each having a shaft and an agitating means to accomplish the purpose of the invention.

In Figs. and 6 another form of the apparatus is illustrated comprising a shell 22 di vided by partitions 23 and 24 and having a cover 25. Shafts 27 and 28 extend longi tudinally over the compartments and are provided with pulleys 29 whereby they may be rotated .by the application of power from any suitable source. The shafts 27 and 28 carry bevel pinions 30 which mesh with corresponding gears' 31 on a plurality of vertical shafts 32. The latter are supported in the respective compartments and are provided with propellers 33 which being rotated "cause a constant agitation of the solution.

The several compartments are connected by semi-cylindrical overflow pipes 34 which introduce the liquid overflowing from each compartment into the succeeding compartment atthebottom thereof. The solution is introduced to similar devices 35 and 36 which del ver the solutions and reagents atthe bottom of the first compartment of each series. The

last compartment of each series is provided.

with an overflow 37 through which the mix ture of, solution and precipitate escape to the respective thickener. By the arrangement described movement of the solutions and precipitates through the apparatus is carried out in such a way as to ensure thorough agitation thereof and the maintenance of the reacting materials for a suflicient period in each of the compartments.

, 101m of the advantages of the process as described is the possibility of carrying out the operation continuously to produce the desired" precipitataThe major advantage, however, is "the possibility of securing the precipitate substantially free from contaminating ingre'dients' derived either from the solution or from the'reagent. It is possible by the application of the invention to conduct the separation of constitutents from solutions in a rapid and effective manner, thus permitting the commercialproduction of various materials more cheaply than has been possible heretofore.

Various changes may be made in the details of operation as herein indicated and in the apparatus used therefor without departing from the invention or sacrificing any ofthe advantages thereof.

-I claim:

1. The method of separating tin compound, and utilizing the precipitate fromthe second step as the reagent in the first step of the method.

' .2. The method of separating tin compounds from solutions involving the addition of areagent to the solution to precipitate'the tin compound, which comprises add ing thereagent in successive steps with intermediate separation of the precipitate, the quantity of the reagent used in the first step being approximately half the theoretical quantity required to precipitate all of the tin.

compound and-the quantity of the reagent used in the secondstep being ap roximately the theoretical quantity require tate all of the tin compound.

3. The method of separating tin compounds from solutions involving .th'eaddito precipition of the reagent to the solution to precipitate the tin compound, which comprises adding the reagent in successive steps with intermediate separation'of the precipitate, the

quantity of reagent usedin -the first step being approximately half the theoreticalquantity required to-precipitate all of the tin compound and the quantity of reagent used in the second step being approximately the theoretlcal quantity required to precipitate all of the tin compound, and utilizing the precipitate from the second step as the reagentin the first step of the method. y

4. The method of separating t1n compounds from solutionsinvolving the addition of a reagent to the solution to. precipitate the tin compound, which comprises adding a portion only of the reagent required to precipitate all of the tin compound, vseparating the precipitate, adding to the solution a quantity of the reagent suific'i'ent'to precipitate all of the tin compound in the original solution, separating the precipitate from thesecond step and utilizing it as the reagent in the first stepofthemethod. v .f

5. The method of separating tin compounds from solutions involving the addltion'ofa reagent to thesolutio'n to precipi-- tate' the tin compound, which comprises adds ing approximately half of the reagent .required to precipitate all of the tin compound,

separating the-precipitateand adding to the:

solution a quantity of the reagent suiiicient to precipitate all of the tin compound in the original solution.

6. The 'method of separating tin 'compounds from solutions invelving the: addi-' tion of a reagent to the solut on'to preclpltatethe .tin compound, which comprises adding approximately half of the reagent requlred to precipitate all of the 'tin compound, sep- 'arating the precipitate, adding to the solution a quantity. of the reagent suflicient to precipitate all .of the "tin compound in the original solution, separating the precipitate from the second step and utilizing 'it as the reagent in the first step of the method;

7. The method of separating tin com pounds from solutions involving the addition of a reagent to the solution to precipitate the tin compound, which comprises precipitatin and removing a portion of the tin compoun adding to the solution a sufiicient excess of the, reagent to avoid separation of impurities therefrom; separating the precipitate from the second step and utilizing it as the reagent in the first step of the method.

, In testimony whereof I afiix my signature.

HENRY M. SOHLEICHER, 

